Radio transmission system



June 29 1926. 1,590,374

L. c. F. HORLE RADIO TRANSMISSION SYSTEM Filed Jan. 16, 1926 I: "1| l l NM HP film 1| I I Illl lb l w 91: 0

- INVENTOR Lawrence C. F Hor/e ATTORNEY station has carried only the audio frequency Patented June 29, 1926.

UNITED STATES PATENT OFFICE.

LAWRENCE C. F. HORLE, OF NEWARK, NEW JERSEY, AS SIGNOR TO FEDERAL TELE- PHONE MANUFACTURING CORPORATION, OF BUFFALO, NEW YORK, A CORPORA- TION OF NEW YORK.

RADIO TaANsMIssIoN SYSTEM.

Application filed January 16, 1926. Serial No. 81,626.

This invention relates to radio transmission systems and more particularly to a transmission .system in which a number of radio broadcasting stations are arranged for simultaneously radiating speech signals or other signals originating in a single master control station connected by line wires to the broadcasting stations.

The present application is a continuation in part of my application Serial No. 7 30t85, filed Aug. 6, 1924.

It has been proposed heretofore to broadcast speech or other radio signals, originating at a central master station,,simultaneneously from widely separated stations by transmitting to all of the broadcasting stations the speech or other signal wave over line wires from the master station, each station of the group of broadcasting stations generating its own individual carrier wave, independentlyof the master station, and the carrier wave of any given station having a wave length different from that of others of the group. In such systems the energy received over the line wires from the master speech or signal wave-Which has then been impressed upon the various carrier Waves of the broadcasting stations as a modulating component of these carrier waves. 1

It is frequently desirable, however, that the speech or other signals thus originating in a master station and transmitted over line wires to a group of radio broadcasting stations be radiated from all the members of the group of broadcasting stations on carriers of the same, instead of difierent, wave length for the individual stations of the group. But in order that such broadcasting of the same speech 'or other signal on the same carrier wave length from a number of stations simultaneously may be accomplished satisfactorily, it is imperative that the wave lengths of the carriers radiated from the individual members of the broadcasting group be maintained identically the same. If these carrier wave lengths from the respective stations are permitted to differ, reception of the broadcast radio signals by a receiver so situated as to be within the broadcasting range of more than one of the group of stations becomes difiicult or impossible, because of beats due to the difierence in'wave length of the carriers radiated from the various stations.

To obviate this difficulty in reception of the broadcast modulated signal waves from the group of stations, it is proposed to provide an arrangement such that the energy transmitted over line wires from the master station may not only act to modulate the carrier waves of the several broadcasting stations with a speech or other audible component but may also act as a control means so related to thet'ransmitting means at the several stations of the broadcasting group that the carrier waves radiated from the said several stations are maintained at the same frequency each to each. This control of broadcasting frequency of the carrier waves radiated from anumber of interconnected stations by means of energy transmitted over line wires from a distant master control station cannot, however, be attained by the direct transmission, over the wires, of a carto causes well recognized in the art, such as attenuation and distortion which increase with the frequency. Further, it is obvious that the problem of maintaining the frequency of the carrier waves radiated from the several stations equal each to each is alsc not to be solved attempting to change the frequency of these broadcasting carrier waves to meet the conditions imposed by transmission over long line wires, since this procedure means a reduction of the broadcastingfrequency to the frequency suitable to line wire transmission, and consequently to a point far below that required in practice for radio telephony. The solution of the, problem, therefore, of so controlling, over line wires, the carrier waves of a group ofbroadcasting stations from a distant master control station as to hold the frequencies of these broadcasting carrier'waves identically the same, calls for means and methods which permit the full use of such line wire carrier Wave frequencies, say 10000 to 20000 cycles, as have been found efficient in line wire transmission, and at the same time it calls for means and methods which makev possible the generation and use of broad-- casting carrier Waves, with the frequency under control of the master control station and the same for all stations of the group, of the enormously high frequency, tending toward still higher values at the presenttime, now usual and required in radio broadcasting practice.

The primary object of the present invention is to provide a system in which may be retained all the advantages inherent in the usual methods of simultaneous broad casting on different wave lengths from several stations of the speech or other signals transmitted over line wires from a master station, and in which, further, may be fully realized the advantages inherent in the method of broadcasting, simultaneously from such groups of stations, on the same wave length.

In accordance with the invention, energy in the form. of a line wire carrier wave, of a frequency best suited to line wiretrans- .mission, is sent over line wiresto the several stations of the broadcasting group. This line wire carrier wave is impressed upon suitable means at .each of the stations, by which the wave is amplified, and changed in frequency to the high value required for broadcasting, the frequency of the broad casting wave being, .however, maintained the same for all members of the group of broadcasting stations. At some point in the carrier wave path through the complete system'of master control station andbroadcasting station, the carrier wave is modulated by a speech or other audio frequency signal wave provided through the action of suitable means in the master control station. The amplified and -modulated high frequency waves are finally radiated in the usual manner simultaneously from the several stations of the broadcasting group.

The invention will be best understood as to organization and method of operation and as to its other objects and advantages by reference to the following detailed description and to the drawing, which illustrates one embodiment of the invention.

The figure represents schematically an embodimentof the invention in which a speech or other audio frequency signal wave and a line wire unmodulated carrier wave are separately transmitted from control station to broadcasting station.

casting stations comprises the following apparatus represented schematically in the figure: Speech or other signal supply wave amplifier 6 line carrier wave distortion amplifier 7; wave filter 8; radio frequency amplifier 9 modulator and radio frequency power amplifier 10; transmitting antenna 1.1. Line wires 12 connect the line carrier Wave generating apparatus 3 of the master control station 1 to the llne carrier wave d1stortion amplifier 7 of a broadcasting sta-' n carrier wave is transmitted in a usual manner over line wires 12 to distant broadcasting stations such as 4 and 5. At a given broadcasting station the wave. of line wire carrier frequency, is distorted by any well known and suitable means as by a distortion amplifier 7 to produce a desired hermonic frequency of the said incoming line wire carrier wave. This desired harmonic is selected by Wave filter 8 through which the wave from the distortion amplifier is passed.

The frequency of the line carrier wave transmitted over the line wires 12 and used as a basis for the harmonic is sochosen that the said harmonic is of the frequency desired for the radio frequency wave which is to be broadcasted from the station. The radio frequency carrier wave resulting from the selective action of wave filter 8 is suitably amplified as by R. F. amplifier 9. The modulation of this radio frequency carrier wave from amplifier 9 is effected by means of a speech or other audible signal wave transmitted from audible signal wave generator 2, over line wires 13, through audible signal amplifier 6 to the modulator and R. F. power amplifier 10. In this modulating and amplifying apparatus 10 the amplified audible signal wave is impressed upon the amplified R. F. carrier wave, and the resulting modulated R. F. wave is then broadcasted in the usual manner from antenna 11.

The schematic drawing is representative of an embodiment of the invention in that it shows the several conversions that go on in the system. It is to be understood, however, that in practice various additions to the apparatus illustrated may be made, such .for. example as many stages of amplification where necessary. It is to be further understood that such additions, and likewise many changes in the apparatus described afnd illustratedmay be made without departin ""fromthe scope of the invention as define in the claims.

What is claimed'is: 1. The method of radio transmission which comprises generating at a control station a carrier wave of frequency above audibili-ty but of the comparatively low order of frequency of line wire carrier waves, trans-- mitting the carrier Wave over line wires to a radio transmitting station, changing the frequency of the line wire carrier wave at the radio 'transmitting'station to (produce a radio carrier wave of frequency highrelatively to that of the line wire carrierwave, and modulating the radio carrier wave eso at the radio transmitting station by a wave of signal frequency generated at said control station. u I i 2. A. radio transmitting system compris ing a control station and a radio transmitting station, means at the control station for generating a line wire carrier wave, means comprising line wires for transmitting the carrier Wave to the radio transmitting sta tion, means at the radio transmitting station forincreasing the frequency of the line wire carrier wave to produce a radio carrier wave of comparatively high frequqncy relatively to that of the line carrier wave, means at the control station for generating a wave of signal frequency, means comprising line wires for transmitting the signal frequency Wave to the radio transmitting station, and means at the radio transmitting station for modulating the radio carrier wave by thesignal frequency wave.

3. The method of radio transmission which comprises generating at a master control station a carrier wave of frequency above audibilit but of the comparatively low order 0 frequency of line wire carrier waves, transmitting-the carrier wave over line Wires to a plurality of radio transmitting stations, changing the frequency of thewaves and of such frequency that a given harmonic of said wave will be of a desired radio frequency, transmitting the carrier Wave over line W11GS to a plurality 'of radio transmitting. stations, distorting the wave at each transmitting station to produce harmonics of said wave,- increasing the frequency of the carrier wave to the same degree at each of the transmit Q ting stations to produce at each station a radio carrier wave of frequency comparativelyhigh felatively to that of the line wire carrier wave by filtering out a desired harmonic oflthe line wire carrier wave, and modulating the radio carrier wave at each radio transmitting station by a wave of signal'frequency generated at said master con trol station.

5. A* radio transmission system comprising a master control station and, a plurality of radio. transmitting stations, means at the control station for generating a line wire carrier wave, means comprising line wires for transmitting the, carrier wave to each radio transmitting station, means at each of the radio transmitting stations for increasing to the same degree the frequency of the line wire carrier wave to produce at each station a radio carrier wave of comparatively high frequency relatively to that of 7 the line. carrier Wave, means at the master control station for generating a wave of signal frequency, means comprising line wires for transmitting the signal frequency wave to each radio transmitting station, and means at each radio transmitting station for modulating the radio carrier wave, by the signal frequency wave.

6. A radio transmission system comprising a master control station and a plurality of radio transmitting stations, means at the control, station for' generating a line wire carrier wave, means comprising line wires for transmitting the carrier wave to each radio transmitting station, distortion means at each of the radio transmitting stations for produning harmonics of the line carrier Wa"e,'means at each of the radio transmitting stations for increasing the frequency of said Wave to the same degree to produce at each station a radio carrier wave of com-v paratively high frequency relatively to that of the line carrier wave by filtering out a desired harmonic of the line carrier wave,

means at the master control station for generating a wave of signal frequency, means comprising line wires for transmitting the signal frequency wave to each radio transmitting station, and means at each radio,

transmitting station for modulating the radio carrier wave by the signalfrequency wave. in

Inwitness whereof, I hereunto "subscribe my name.

LAWRENCE O. F. HORLE. 

